The 53-year-old television producer is believed to have declined Cole's invitation to join her Los Angeles birthday bash tonight (Sunday).

Speaking to The Sunday People, a source said: "She sent an invitation to Simon as she genuinely wanted him there.

"He's been a big part of her life and, despite their falling out, she sees him as an old friend who she was very close to once. She was hoping he'd make it so is a little disappointed he won't be there."

The source continued: "She has put all their differences aside and moved on in her life. The party is going to be one of the most memorable occasions and she carefully chose who she invited. Unfortunately though Simon wasn't able to make it."

Cole previously expressed her excitement about turning 30, saying: “I look up to women in their 30s and think, ‘This is when women are at their most beautiful, their most sexy’.”